1. Technical Field
The present invention relates to a fluid coupling composed of a socket and a plug.
2. Description of the Related Art
FIG. 18 shows a state in which a plug 1 and a socket 2 of a conventional fluid coupling described in Japanese Patent Laid-Open Application Nos. 2002-295770, 2001-124277 are combined and FIG. 19 shows a state in which the plug 1 and the socket 2 are separated from each other.
As shown in FIG. 19, the plug 1 has a cylindrical structure in which a fluid passage is formed in the inner surface thereof. A female screw 3 is formed in the inner surface at an end (left end in FIG. 19) of the plug 1 and a pipe is connected to this portion by thread coupling. A valve seat 4 is formed in the inner surface at the other end (right end in FIG. 19) of the plug 1. A holder stopper 5 is mounted in the center of the inner surface of the plug 1. A steel ball engagement outer peripheral groove 6 is formed in the center of the outer surface of the plug 1.
The socket 2 has a cylindrical structure in which a fluid passage is formed in the inner surface thereof and configured of a main body portion 7 on the right side and a plug insertion portion 8 on the left side in FIG. 19.
A female screw 9 is formed in the inner surface at an end (right end in FIG. 19) of the main body portion 7 of the socket 2 symmetrically with the plug 1 and other pipe is connected to this portion by thread coupling. A valve seat 10 is formed in the inner surface at the other end (left end in FIG. 19). A holder stopper 11 is mounted in the center of the inner surface of the main body portion 7.
The plug insertion portion 8 of the socket 2 has a bore to which the plug 1 is to be fitted. A stopper 8a is formed in the outer surface near an opening end (left end in FIG. 19) of the plug insertion portion 8 and a plurality of holes 12 are formed, so that steel balls 13 are accommodated in the holes 12. An O-ring 15 is mounted in an inner peripheral groove 14 formed in the center of the inner surface of the plug insertion portion 8. A sleeve 16 is fitted to the outer peripheral face of the plug insertion portion 8 and urged toward an opening end (left end in FIG. 19) by means of a spring 17. When the sleeve 16 is urged toward the opening end so that it makes contact with the stopper 8a, the inner surface of the sleeve 16 presses the steel balls 13 so that the steel balls 13 are projected into the interior of the plug insertion portion 8. When the sleeve 16 is moved in an opposite direction to the opening end or in the direction of arrow A, the steel balls 13 are retracted into the inner peripheral groove 18 formed in the inner peripheral surface of the sleeve 16.
The plug 1 and the main body portion 7 of the socket 2 each contains a valve 19, a valve holder 20 and a spring 21. The valves 19, valve holders 20 and springs 21 have the same configuration each and are disposed symmetrically. Accordingly, the valve 19, the valve holder 20 and the spring 21 of the plug 1 will be described and description of those of the socket 2 is not described.
The valve 19 is composed of a valve main body portion 22 which makes contact with the valve seat 4 of the plug 1, a projecting portion 23 which is projected outward of the opening end of the plug 1 from the vale main body portion 22 and a valve shaft 24 which is projected inward of the plug 1 from the valve main body portion 22. The outer peripheral face of the valve main body portion 22 is formed in a conical face and a valve packing 26 is mounted in an outer peripheral groove 25 therein.
The valve holder 20 is made of sintered metal and as shown in FIG. 20, configured of an annular portion 27, a cylindrical portion 28 which is located inside the annular portion 27 and longer than the annular portion 27 in the direction of a fluid passage, and a plurality of supporting portions 29 which connects the inner surface of the annular portion 27 with the outer surface of the cylindrical portion 28. The valve holder 20 is inserted into the interior of the plug 1 so that the annular portion 27 makes contact with the holder stopper 5 mounted on the inner surface of the plug 1, thereby the valve holder 20 being prevented from slipping out in the leftward direction in FIG. 19. A valve shaft 24 of the valve 19 is inserted into the interior of the cylindrical portion 28 so as to support the valve 19 such that it is slidable in the axial direction.
The spring 21 is made of a straight type coil spring and mounted on the cylindrical portion 28 of the valve holder 20 and the valve shaft 24 of the valve 19 in a compressed state, thereby urging the valve 19 such that the valve main body portion 22 of the valve 19 makes contact with the valve seat 4.
To connect the conventional fluid coupling having the above-described structure, as shown in FIG. 19, the sleeve 16 of the socket 2 is moved in the direction of arrow A resisting the urging force of the spring 21. When the plug 1 is inserted into the plug insertion portion 8 of the socket 2 with this condition, the steel balls 13 of the socket 2 are pressed by the outer peripheral face of the plug 1 and retracted into the inner peripheral groove 18 of the sleeve 16. Consequently, the plug 1 can be inserted into the plug insertion portion 8 of the socket 2. When the plug 1 is inserted up to the deep side of the plug insertion portion 8 of the socket 2, the projecting portion 23 of the valve 19 of the plug 1 presses the projecting portion 23 of the valve 19 of the socket 2. As a result, as shown in FIG. 18, the valve 19 of the plug 1 and the valve 19 of the socket 2 are retracted while pressing each other, so that the valve main body portion 22 leaves the valve seats 4, 11, so as to open the fluid passage, thereby allowing fluid to move. When the sleeve 16 is returned to an opposite side to the direction of the arrow A, the steel ball 13 leaves the inner peripheral groove 18 of the sleeve 16 and is pressed by the inner peripheral face of the sleeve 16, so that it is projected into the interior of the socket 2 from the hole 12 and engaged with the outer peripheral face of the plug 1 and then locked. Accordingly, the plug 1 is prevented from pulling out of the plug insertion portion 8 of the socket 2. Further, a gap between the plug 1 and the plug insertion portion 8 of the socket 2 is sealed with the O-ring 15 fluid-tightly.
To release coupling of the plug 1 and the socket 2, the sleeve 16 is moved in the direction of arrow A from a state shown in FIG. 18 and the plug 1 is pulled in the direction of separating the plug 1. Consequently, the steel ball is retracted into the inner peripheral groove of the sleeve 16 and unlocked, so that the plug 1 can be pulled out. When the plug 1 is separated from the socket 2, the valves 19 of the plug 1 and the socket 2 are urged by the springs 21 and advanced. Then, the valves 19 come into contact with the valve seats 4, 10 and consequently, the opening ends are closed fluid-tightly and sealing between the plug 1 and the socket 2 by the O-ring 15 is released. As a result, the plug 1 can be removed from the socket 1 without any fluid leakage.